Manufacture of alkyllead compounds



Patented Dec. 26, 1950 MANUFACTURE OF ALKYLLEAD COMPOUNDS George Calingaert and Hymin Shapiro, Detroit, Mich., assignors to Ethyl Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application July 28, 1949, Serial No. 107,385

This invention relates to a catalytic process for the manufact re of alkyllead compounds.

More specifically it is directed to an improved process for the manufacture of tetraethyllead.

I The process employed in present commercial practice for the manufacture of tetraethyllead has been in use for a number of years and, in general, is satisfactory. However, it has certain disadvantages which are overcome by practicing our invention. The present commercial process proceeds by reacting a sodium-lead alloy, of composition controlled to correspond substantially to NaPb, with ethyl chloride according to the following equation:

It will be noted in the above equation that four molecules of sodium chloride are formed for each molecule of tetraethyllead produced, and while all the sodium is converted to the chloride, there remains unreacted '75 per cent of the lead originally present in the sodium-lead alloy. In actual practice, under the best conditions obtainable, only 22 per cent of the lead is alkylated, and the remainder must be recovered and reprocessed to NaPb alloy in order to make the operation economical. A further disadvantage of such a large quantity of unreacted lead is that valuable space in the reaction vessel is occupied by materials which are essentially inert for the manufacture of tetraethyllead under present conditions and mode of operation.

Various other processes, employing alloys containing greater quantities of sodium than correspond to the composition NaPb, have been proposed in order to overcome these obiections to the foregoing commercial process. Their purpose is to convert a greater proportion of the lead present in the alloy to alkyllead compounds. However, these methods are subject to the serious disadvantage that the ratio-of sodium to lead for each of the alloy compositions must be maintained within extremely narrow limits, as otherwise the lead is inactive and will not satisfactorily react with the alkylating agents. Slight deviations from these narrow limits in the sodium-tolead ratio not only reduce the conversion of lead to alkyllead, but if the deviation is great, the reaction with the alkylating agents practically ceases, for reasons not c early understood. Thus the choice of a sodium-lead'alloy is restricted to a few specific compositions.

Somewhat more flexibility is obtainable in certain of these prior art processes by utilizing bromide and iodide alkylating agents, although even 7 Claims. (01. 260i37) with these the limits of alloy composition for good operation are narrow. A further disadvantage of the employment of alloys high in sodium, in a large scale process, is the possibility of a shortage of metallic sodium. A still further disadvantage of many such proposed processes is the high temperature required for operation.

It is therefore an object of our invention to provide a new and improved process for the manufacture of alkyllead compounds which overcomes the above objections. A further object is to produce tetraethyllead and related compounds by a process which can convert a surprisingly large amount of the lead charged to the reaction into the desired end product, thereby avoiding the expensive reprocessing of large quantities of lead. Another object is to increase substantially the yield of tetraethyllead while using the existing equipment of the present commercial process. A still further object is to produce tetraethyllead in large quantities, without the consumption of correspondingly 1arge quantities of metallic sodium.

We accomplish these objects, and others which will be apparent from the discussion of our inven tion which follows, by adding magnesium to a sodium-lead alloy, in a suflicient quantity to activate it, thereby enabling it to react readily with an alkylating agent, such as an alkyl chloride, in the presence of a catalyst, such as an alkyl ether.

We have found that to produce alkyllead compounds under conditions which are practical for commercial operation and from materials which are not prohibitive in. cost, it is unnecessary to be restricted to the few sodium-lead alloys of the prior art. On the contrary, we have made the surprising discovery that alkyllead compounds can be produced by the alkylation of sodium-lead alloys having a wide range of sodiumto-lead ratios, provided these alloys contain sufficient magnesium to activate them. Thus, the proportion of lead converted to alkyllead compounds can be controlled within an unexpectedly broad range. Further, the amount of sodium required for any given yield of alkyllead compound can, if desired, be considerably less than that to which the present commercial process is limited.

Furthermore, in our process, owing to the flexibility of choice of alloy composition, the ratio of sodium to magnesium to lead'can be adjusted to obtain optimum efiicien-cy of utilization of the sodium and magnesium. Such high efficiencies in the use of these metals may be at the expense of the alkyllead yield, but this, under some condigreater importance than high lead utilization.

The proper evaluation of an alloy for commercial use involves many factors intimately connected with the economics of the operation. Among such factors may be mentioned the availability and size of equipment, the product output desired, the absolute and relative cost and availability of sodium, magnesium and lead, and the cost of recovery of unreacted lead. It should be noted that sodium, in the present commercial practice, as well as both sodium and magnesium in the process of our invention, are degraded to forms which represent only a small fraction of the value of these metals in the free state, whereas the lead so produced may be recovered by methods which are not prohibitive. Thus, it will be apparent that the almost complete freedom of choice to select the alloy composition in accordance with economic considerations is an outstanding advantage of this invention.

The process of our invention is more readily understood by a consideration of the following equation, which, while directed tothe production of tetraethyllead, applies equally to alkyllead compoundsin general:

As pointed out previously, the present commercial process at 100% emciency converts four atoms of sodium to sodium chloride, for each molecule of tetraethyllead formed. This relationship obtains in the process of our invention as well, but in addition two atoms of magnesium similarly converted to magnesium chloride will produce a furthermolecule of tetraethyllead. In the above equation when the expression sil 'is equal to unity the lead is entirely consumed,

and as written the equation limits the values of to a maximum value of 1. However, we do not impose this restriction on the composition of the alloys of our invention, and have obtained good results beyond these limits. In this latter case, the right hand side ofthe equation should be written as in which the last term represents the surplus of C2H5 radicals which is converted to hydrocarbon by-products.

As a general rule, our ternary alloys have a composition such that the subscript b is at least 0.2 but less than 3, and the sum of the subscripts a and b varies between the limits of about 0.5 and 3. We have found that a and b can be varied independently within the limits prescribed for their sum. A ternary alloy of sodium, mag-v nesium and lead in which the sum of a and b is less than about 0.5 contains more than 94.5 parts by weight of lead per 100 parts of alloy. We have found that such alloys resemble metallic lead in their physical properties, in that they possess high malleability and ductility and are difficult v to comminute. For these reasons, alloys in' which I of alkyllead compounds generally, such as tetra- I of the present commercial process.

4 a+b is less than 0.5 are unsatisfactory for commercial utilization and are to be avoided.

In accordance with our process, the more sodium and magnesium alloyed with the lead, the more lead is converted-to alkyllead. However,

' we have found that when the sum of. a and b exceeds 3.0, as a general rule little benefit is gained from further quantities of the sodium and magnesium metals, and the additional yield of tetraalkyllead is small and is obtained by decreasing the efliciency of utilization of the sodium and magnesium. Therefore alloys in which the sum of a+b exceeds 3 are generally to be avoided.

We have determined that the incorporation of substantial amounts of magnesium into sodiumlead alloys unexpectedly activates the alloy, permitting alkylation of the lead in the presence of a catalyst, without regard to the sodium-lead ratio. However, when the amount of magnesium is reduced below a quantity such that the subscript b is less-than about 0.2, it appears The proportions of sodium, magnesium and lead in the activated alloys of our invention can be describedalso in terms of the percentage by weight of each of these metals. Thus, we have found that alloys having, on a weight percentage basis, up to-22.5 sodium, at least 2.5 and less than 25 magnesium, and up to about lead, are satisfactory in'practicing the process of our invention. The amounts of sodium and magnesium, which can be referred to as secondary metals, can be varied independently within these prescribed limits, so long as their sum remains within the limits of about 5.0 and 25 per cent by weight of the total alloy.

By practicing our invention, yields of alkyllead compounds of-50per centand higher have-been obtained, based on the lead charged to the reaction zone. This constitutes more than a twofold increase over-the present commercial process. This excellent conversion of lead to alkyllead compounds has been accompanied by a v94 per cent efficiency of utilization of the secondary metals sodium and magnesium. i

This invention is adaptable to the production ethyllead, tetramethyllead, dimethyldiethyllead, triethylphenyllead and tetrapropyllead. Nevertheless, for convenience, specific reference hereinafter will be made to tetraethyllead, the most widely known alkyllead compound. Whenever in the following description this material is referred to,- it is to be understood that other alkyllead compounds and mixtures thereof, are .also intended, in the same manner as though specifically referred to. Further, whenever in the following descriptionreference'is made. to ethyl chloride as the ethylating agent, it is to be understood that other ethylating and alkylating agents canbe-substituted therefor or used-in. admixture therewith. a

Generally, our invention is practiced as follows: the comminuted ternary alloy consisting of the magnesium-activated sodium-lead alloy is placed in a reaction vessel such as the autoclave The vessel is then closed except for the liquid feed line through which the fluidv reactants are passed. The necessary quantity of an alkylating agent such as ethyl chloride is then introduced into the autoclave, followed by delivery 'of a catalyst such as diethyl ether, or: the latter can be added along with theethyl chloride. In the former method, the time interval between the addition oi? the alkylating agent and the catalyst can be short or long.

A large number of ouralloys undergo little or no alkylation except in the presence of a catalyst. For such alloys it is preferred to add the catalyst along with the alky-lating agent orimmediately thereafter. This mode of operation is hereinafter referred to as the one-stage process.

' Some of ouralloys are able to react with the alkylatingagent in the absence of a catalyst, but a marked increase in yield occurs when a catalyst is subsequently added. For these alloys it is possible to produce a non-catalytic reaction between the alloy and the alkylating agent in the first stage, followed by the addition ofcatalyst, which produces a catalytic reaction, with the formation of additional alkyllead, in the second stage. This operation is hereinafter referred to as the -two-stage process. It has certain advantages, among which is the ease of control of the overall reaction, particularly the catalytic reaction. The two-stage process also permits the reaction rate, heat transfer, and operating time cycle to be controlled bymeans of the rate at which the catalyst is added to the principal reactants.

Variations in the above processes can be made. such as introducing part of the catalyst along with the initial feed of the alkylating agent, followed by additional catalyst. Also, While it is possible in our two-stage process to add only a limited amount of alkylating agent for the first non-catalytic stage and then add an amount s-u-flicient to complete the. reaction in the second stage, it is possible to. add most or all of the alkylati-ng agent in the first stage. It should be noted that while the. presently used commercial process proceeds to completion without a catalyst and is essentially non-catalytic, our reaction is essentially catalytic and requires a catalyst for the full utilization of the alloy.

In the. working exampes of our invention which follow, the yield of alkyllead compound will be. based on the lead present in the. ternary. alloy. employed, unless otherwise specified. Also, unless. otherwise stated. all parts and percentages herein are. by weight. Further, other means diethyl ether unless otherwise specified.

Example I One stage reaction using sodium-magnesiumlead alloy, ethyl chloride and other: A charge of 100 parts. of sodium-magnesium-lead alloy consisting of 9.5 parts sodium, 5.7 parts magnesium and 84,8 parts of lead is added to the reaction vessel equipped with an agitator, a jacket for circulation of heating or cooling liquids, a reflux condenser, charging and discharging ports, liquid feed lines, and means for releasing the pressure. A mixture of alkylating agent and catalyst: consisting of 130 parts of liquid ethyl chloride and 5 parts of other is added under pressure to the stirred alloy in the vessel over a period of one-half hour. By controlling the flow of liquid in the autoclave jacket and in the reflux condenser, the temperature of the reaction mass is permitted to risefrom the initial temperature of 50 G; to a temperature of 85 C. during this feed. The pressure in the autoclave during this period is allowed to rise to about 85 pounds per square inch gauge. The stirred reaction mass is maintained at a temperature of 85 C. and a pressure of 85 pounds for an additional two and one-half hours. This period is referred to as the cooking period. At the end of this period the pressure in the autoclave is reduced to atmospheric by venting for 15 minutes, while the temperature is maintained at 85 C. For an additional 15 minutes nitrogen is passed over the reaction mass while the autoclave is open to the atmosphere. With a stream of nitrogen passing through the reaction vessel the mass is cooled to C. over an additional 30-minute period. Thus a total reaction time of fourhours is employed. The reaction mass is then discharged from the reac-- tion vessel and steam distilled or otherwise treated to recover the alkyllead product. The

yield of product is 66.2 parts, or a yield of Expressed in another way, the yield is 94% based on the combined sodium and magnesium present in the sodium-magnesium-lead alloy.

Example, {I

Two-stage reaction using sodium-magnesium! lead alloy, ethyl chloride, and ether: Using sub.-v stantially the same operating procedure as d e-H scribed in the above example, a two-stage modification is carried out by adding 100 parts of a sodium-magnesium-lead alloy consisting of 9.6 parts of sodium, 5.6. parts of magnesium and 84.8 parts of lead, with the variation that. all the ethyl chloride is added to the. system while the temperature is permitted to rise to 70 C. After a total contact time of one hour with ethyl chloride alone, 5 parts of. other is added and heating is continued to maintain the temperature at 70 C. for an additional hour. The cooking, venting, cooling, discharging and recovery of the product are continued as in Example I. The total yield of product is, 5.1.6 parts, or 39%.. It is 73%, based on the total amount of sodium and magnesium present in the sodium-magnesium-lead alloy.

Example HI Using substantially the same operating procedure as described in Example I, a one-stage modification of our process was carried out, with the. variation that the amount of, catalyst employed is 15 parts per parts of alloy. The alloy composition consists of 610* parts of sodium, 15.0 parts. of magnesium, and 79.0 parts of lead.

A mixture of parts of ethyl chloride and 15 parts of other are added together. A total reaction time of four hours at 100 C. is employed. The yield of product is 58.5 parts, or 47.5 per cent.

Example I V- Example I is repeated for a period of four hours at a temperature of 70 C. using 100 parts of an alloy consisting of 0.5 partof sodium, 102 parts of magnesium and 89.3 parts of lead, in the presence of 5 parts of ether. With this alloy the yield of product is 48.4 parts, or 34.7 per cent.

Example V 75 This may be accomplished by first mixing toing them continuously through a reactor under suitable reaction conditions.

By means of our invention most of the catalyst and the excess alkylating agent can be recovered. Part is recoverable during and after the reaction by venting or other means, and part during the recovery of the alkyllead product. During the alkylation process the pressure is controlled by venting the by-product gases, and this releases part of the ether along with excess ethyl chloride, both of which may be recovered by condensation. Additional quantities of ether and excess ethyl chloride are recoverable. during the separation of the alkyllead' product by steam distillation, solvent extraction or other suitable means.

In addition to the above examples, we carried out a number of ethylations under uniform conditions, with the results set forth in the following table. In columns 1, 2 and 3 is listed the composition of the sodium-magnesium-lead alloys.

The yields obtained with each alloy are listed in columns 4 through 7. The yields tabulated in columns 4 and 5 represent the percentage of the lead present in the alloy which is converted to alkyllead compound, while columns 8 and 7 give the yield on the basis of the combined amount of sodium and magnesium present in the alloy. To obtain the tabulated results, a series of examples was carried out for the alloys in the table, simi lar to working Example I. In addition a similar series of examples was conducted for the alloys, but the catalyst was omitted. Thus, columns 4 and 6 list the yields obtained without the'catalyst, while columns 5 and 7 list the yields obtained with the catalyst. The conditions employed for the catalytic reaction were as follows: 100 parts of the ternary sodium-magnesium-lead alloy was reacted for four hours at a temperature of 70 C. with approximately 210 parts of ethyl chloride and 5 parts of diethyl ether. The non-catalytic results were obtained under identical conditions and with identical quantities of alloy and ethyl chloride, but in the absence of the diethyl ether.

Alloy composition, Yield of alkyllead compound, percent parts by weight Based on Pb Based on secondary in the alloy metals in the alloy Na Mg Pb Without With Without With catalyst catalyst catalyst catalyst 8. 8 16. 75. 2 0 18. 7 0 16.1 0.5 24. 0 75. 0.3 10. 6 0.3 10. 6 11.8 12.6 75.6 0 l0. 7 0 10.7 8. 8 l4. 0 77. 2 0 27. 5 0 27. 5 1.6 21.0 77;4 0 19.7 0 19.7 6.0 15.0 79. 0 0.3 28. 5 0. 3 28. 5 12.7 7.7 79.6 1.7 37.4 2.2 48.7 3. 5 16. 5 80. 0 l. 1 23. 4 l. 1 23. 9 15.0 5.0 80.0 4.2 11.3 6.1 16.4 0. 5 l8. 7 80. 8 2. 2 24. 7 2. 2 24. 7 9. 1 9. 8 81. 1 14. l 54. 8 l8. 9 73. 7 6. 0 11. 4 82. 6 8. 6 44. 3 11. 2 58. 1 12. 5 3. 2 84. 3 16. 7 29.0 33. 7 58. 6 0. 5 14. 7 84. 8 0.3 15. 6 0. 4 20. 8 9. 6 5. 6 84.8 18. 9 41. 6 35. 4 77. 6 10.3 3.5 86. 2 19.0 35. 7 44.7 71.2 4. 9 8. B 86.3 6. 2 26.0 11. 1 46. 4 6.0 7.0 87.0 8. 4 27. 6 16. 9 55. 6 3.3 8. 4. 88.3 2.4 15.5 5.0 31.7 0. 5 10.2 89. 3 1. 8 34. 7 3. 6 69.0 5. 5 3.0 91. 5 4. 0 11.9 14. 4 43. 3 0.5 5.3 94. 2 1. 5 13. 4 5.8 53. 4 3. 0 2. 7 94. 3 5. 2 11.4 27.0 58. 6

While our invention is not restricted to any particular class or classes of catalyst, we have found that organic compounds containing an atom capable of chemical coordination with magnesium are particularly eflective. Among these compounds are ethers, organo-ammonium derivatives, and amines. The amount of catalyst is not critical, and may be varied within wide limits, for instance, from 1 to 100 parts of catalyst to 100 parts of lead present in the alloy.

Examples of specific ethers which are effective for use in our process are diethyl ether, methylethyl ether, dipropyl ether, dibutyl ether, dihexyl ether, dimethyl ether of ethylene glycol, 1,4-dioxane and anisole. We prefer to use ethers as the catalyst and particularly the lower alkyl ethers, from methylethyl through dihexyl ether. Illustrative examples of organo-ammonium derivatives are tetraethylammonium iodide, trimethylethylammonium iodide and the like. Among the amines which may be used are triethylamine, trimethylamine, and dimethylaniline. It is to be understood that combinations of the above and related catalysts can be employed with good results.

To illustrate the effects on yield of the amount of catalyst employed, we conducted a series of tests wherein we reacted 100 parts of an alloy consisting of 24.8 parts of sodium, 3.0 parts of magnesium and 72.2 parts of lead, with 180 parts of ethyl chloride, during a reaction time of 4 hours at C. The yields of alkyllead compound were 2.5, 3.8, 28.5, 29.2, 38.3, and 47.0 per cent at diethyl ether concentrations of 0, 5, 15, 30, 50 and parts respectively. Thus we have found that the alloy of this composition does not respond to the presence of catalysts until more than 5 parts per 100 parts of lead is added. In contrast to the foregoing results yields of alkyllead compound of 18.9, 43.1, 41.6, 47.7, 41.4, and'32.6 per cent were obtained under the same conditions with an alloy consisting of 9.6 parts of sodium, 5.6 parts of magnesium and 84.8 parts oflead, and in the presence of 0, 2, 5, 15, 50 and 100 parts of diethyl ether respectively.

Somewhat similar results were obtained with other lower alkyl ethers, with lower tetraalkylammonium iodides, with lower trialkylamines, and with lower dialkylanilines. Excellent results are obtained if the immediately preceding examples are repeated, substituting for the diethyl ether catalyst thereof the following specific catalysts; di-n-butyl ether, 'dihexyl ether, dipropyl ether, methylethyl ether, tetraethylammonium' iodide, tetramethylammonium iodide, triethylamine, dimethylaniiine and trimethylamine.

Various alkylating agents can be employed in our process. The alkylating agents of our invention may be any of those described in the prior art such as alkyl chlorides, alkyl bromides and alkyl iodides. In addition other alkylating agents such as the alkyl phosphates, for example, triethyl phosphate, may be used. For the most part, our alkylating agents are those esters of inorganic acids capable of reacting with the sodium and magnesium in the ternary alloy and having the desired alkyl groups. In general, the inorganic acid ester alkylating agents are the mono-chloro, -bromo and -iodo derivatives of the paraffin hydrocarbons such as methane, ethane, propane, butane and pentane, the corresponding trialkyl phosphates, .etc. For example, methyl bromide, methyl iodide, ethyl chloride, ethyl bromide, ethyl iodide, n-propyl chloride, n-butyl bromide, n-amyl chloride,

n-amyl iodide and triethyl phosphate can-be successfully employed. Instead of or in admix- "9 ture with the normal alkyl halides, their isomers may be used. Various combinations of two or more alkylating agents may be used in the oneand two-stage processes.

To illustrate the effect on yield of alkylating agents, we reacted for 2 hours, at 70 C., 100 parts of a ternary alloy, consisting of 9.6 parts of sodium, 5.6 parts of magnesium and 84.8 parts of lead, with 210 parts of ethyl chloride, in the presence of 5 parts of diethyl ether. A yield of 48.3 per cent of alkyllead compound was obtained, based on the lead present in the alloy. Substitution of 430 parts of n-propyl chloride for the ethyl chloride of this example, and the use of parts of ether, resulted in a yield of alkyllead compound of 20.5 per cent based on the lead employed. Satisfactory results may be obtained by repeating the immediately preceding examples. substituting for t e alkylating agents employed therein the following specific agents: ethyl bromide. ethvl iodide, butyl br mide butyl chloride, tr ethvl nho ph ate and amvl iodide.

To further ill trate thi embod m nt of our invention, we emplo ed ethyl chloride as the alk lating a ent in the first non-catalytic. stage of a twota e operation and methyl iodide as the alkvlatin a ent in the se nd or catalytic sta e. 100 part of a ternary alloy con i ting of 9 6 parts of odium. 5.6 part o ma nes um and 8 8 pa ts of lead wa rea ted for 1 hour at 70 C. with 250 parts of et yl chloride. At the end of th period the eth l chloride was vented off. and 330 parts of meth l iodide and 15 parts of diethyl eth r was ad ed to the reaction ma s from the fir t ta e. The mixture was maintained at a temperature of 70 C. for a period of 3 hours. The yield of alkvllead compound from the combined stages of this process was 33.3 per cent, based on the lead pre ent in t e alloy.

For the be t re ults, the alkylating agents of our proce s s ould be employed in excess of the amount required by the above-described eduation descripti e of our process. If less than the amount of alkylating agent required to completely alkylate the lead according to the above equation is used. the yield will be lower, .but will still be good when determined on the basis of the amount of alkylatin'g agent. To illustrate, a series of example was conducted in which 100 parts of a ternary alloy; consisting -of 0.6 parts of sodium, 5.6 parts of magnesium and 84.8 parts of lead. w a's heated for four hours a temperature of 70 C. with 3-0. 55,125 and 215 parts'of ethyl chloride in the presence-of 5 'p'art s of ether. The yields of alkyllead conrpound were 18.5, 34.5, 45.5 and 45.9 per cent, respectively, based on the lead present. In this example it is to be understood that 30 and 55 parts of ethyl chloride is an insuflicient amount according to the eouation for our process. However. under the conditions herein stated, 36.9 and 34.4 per cent, respectively of th s ethyl chloride was consumed in the formation of the alkyllead compound.

We prefer to introduce the alkylating agent as a liouid. and to conduct our alkylation reaction in the liquid phase. If ethyl chloride is the alkylating agent, the pressure within the autoclave is maintained within the range of about 70 to 125 pounds per square inch. In the same manner, the catalyst preferably is fed into the autoclave in the liquid phase under pressure. If desired the alkylating agent and catalyst can be mixed, and the mixture introduced under pressure into the autoclave.

In general, our process is completed within onehalf 'toeight hours, but for most purposes we employ from 1 to 5 hours. We have observed that there may be a period of no appreciable reaction with certain of our alloys, which we refer to as the induction period, following which the reaction may proceed rapidly. To illustrate this, we reacted 100 parts of a ternary alloy, consisting of 9.6 parts of sodium, 5.6 parts of magnesium and 84.8 parts of lead, with 110 parts of ethyl chloride in the presence of 5 parts of ether. All the ingredients were added to the reaction Vessel at the beginning of the reaction period, and maintained at a temperature of C. The yields of alkyllead compound were 34.7, 40.2, and 50.1 per cent after 1, 2 and 3 hours of heating. respectively. In a similar series of examples an alloy consisting of 9.7 parts of sodium, 3.6 parts of magnesium and 86.7 parts of lead was reacted at a temperature of 70 C. The yields of alkyllead compound were 0.3, 27. 36 and 36 per cent for reaction times of 1, 2, 3 and 4 hours, respectively. Thus in this embodiment of the process of our invention we obtained the maximum yield rapidly after a short induction period.

While the process of our invention is operable over a wide range of temperatures we have found that the preferred temperature for most purposes is within the range of 50 C. to .C. However temperatures as high as 120 C. may be employed in our process. When the two-stage reaction is employed it is sometimes advantageous to operate the second stage at a different temperature than the first. However, temperatures in the neighborhood of 70 C. may be employed in both the one-stage and two-stage operations with excellent results.

To illustrate the effect of temperature on yield we conducted a series of tests wherein 100 parts of a ternary alloy, consisting of 9.6 parts of sodium, 5.6 parts of magnesium and 84.8 parts of lead were reacted with parts of ethyl chloride, in the presence of 5 parts of ether. All ingredients were added to the reaction vessel at the beginning of the reaction. The yields of alkyllead compound obtained after 4 hours of heating were 24.0, 44.4, 52.5, and 32.0 per cent of the lead present, when the temperature of the reaction mass was maintained at 50, 70, 85 and 100 C. respectively. Similarly in a reaction carried out with 100 parts of a ternary alloy, consisting of 0.5 part of sodium, 18.7 parts of magnesium and 80.3 parts of lead, the yield of alkyllead compound was 3.4,- 24.7, and 26.5 per cent when the operation was carried out at 50, 70 and 100 C; respectively.

Our process, in common with most of the processes of the prior art, when employed to make tetraethyllead also produces some hexaethyldilead. Its presence is readily detected by noting the color in the final alkyllead product. If there is no hexaethyldilead present the color is water-white, while a yellow color indicates its presence. In view of the widespread commercial use of tetraethyllead, it may be desirable to convert the hexaethyldilead to it. This may be accomplished merely by heating the product. Actually. by such heating, 82% by weight of tetraethyllead is formed and the free lead so produced can be reprocessed. Further, in our process the formation of hexaethyldilead can be prevented almost completely by employing temperatures near 85 C. or by lengthening the time of the reaction at a lower temperature, say 70 C.

While the foregoing description and examples of the process of our invention relate to the manufacture of tetraalkyllead compounds generally, the preferred embodiment of our invention is the manufacture of tetraethyllead. For this purpose we prefer to employ those ternary sodium-magnesium-lead alloys in which the amount of sodium is less than 14 weight per cent, the amount of magnesium is within the limits of 2.5 and 20 weight percent, and the amount of lead is within the limits of 75 and 90 weight per cent. Also, we prefer to use an excess of the ethyl chloride as heretofore mentioned. Furthermore our preferred catalyst for the manufacture of tetraethyllead is a lower alkyl ether, and in particular we prefer to employ diethyl ether in amounts ranging from 2 to 30 parts by Weight per 100 parts of ternary alloy. Our preferred reaction temperature for tetraethyllead production is between 60 C. and 85 C. at

a reaction time of about 1 to 5 hours.

In the practice of our invention it is advisable to follow the usual precautions in reactions of this type, and avoid the presence of excessive amounts of water.

It is evident from the numerous working examples described above that this invention may be varied within relatively wide ranges, both with respect to the reactants and the operating conditions, without departing from the scope thereof. From the instructions given, those skilled in the art will have no difliculty in selecting the best reactants and operating conditions for any desired purpose.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope hereof, it is to be understood that we do not restrict ourselves except as defined in the following claims.

We claim:

1. In a process for making lead alkyl compounds by reacting a alkylating agent with a sodium-lead alloy, the improvement comprising;

first alloying at least about 2.5% by weight of magnesium with such sodium-lead alloy to activate it and then reacting said ternary alloy in the presence of an alkylating catalyst having an atom which chemically coordinates with magnesium.

2. A process for making lead alkyl compounds which comprises alkylating a sodium-magnesiumlead alloy containing more than 0.2 atom of magnesium for each atom of lead in the presence of an alkylating catalyst having an atom which chemically coordinates with magnesium.

3. A process for making lead alkyl compounds which comprises alkylating a sodium-magnesiumlead alloy having a composition corresponding to NaaMgbPb in which the sum of a and b is within 12 the limits of approximately 0.5 and 3, and b is a least 0.2 in the presence of an alkylating catalyst having an atom which chemically coordinates with magnesium.

4. A process for making lead alkyl compounds which comprises alkylating a sodium-magnesiumlead alloy having a composition corresponding to NaaMgbPb in which the sum of a and b is within the limits of approximately 0.5 and 3, and b is at least 0.2, said reaction being conducted at a temperature between approximately C. and 100 C., for a time between approximately one-half hour and 8 hours in the presence of an alkylating catalyst having an atom which chemically coordinates with magnesium.

5. A process for making tetraethyllead whic comprises ethylating in the presence of a lower alkyl ether a sodium-magnesium-lead alloy having a composition corresponding to NasMgbPb in least 0.2, said reaction being conducted at a tem-'.

perature between about C. and about 85 C., for a time between about 1 and 5 hours.

7. A process for making tetraethyllead which comprises reacting an excess of ethyl chloride' in' the presence of diethyl ether with a sodiummagnesiumdead alloy in which the percentages by weight are less than 14 for sodium, between about 2.5 and 20 for magnesium, and between about and 90 for lead, said reaction being conducted at a temperature between about 60 C.-

' and about- C. for a time between about 1 and The following references are of record in the file of this patent:

' UNITED STATES PATENTS Number Name 1 Date 1,658,544 Youtz Feb. 7, 1928 1,661,809 Monroe Mar. 6, 1.928 2,000,069

Downing et a1 May-7, 1935 

1. IN A PROCESS FOR MAKING LEAD ALKYL COMPOUNDS BY REACTING A ALKYLATING AGENT WITH A SODIUM-LEAD ALLOY, THE IMPROVEMENT COMPRISING FIRST ALLOYING AT LEAST ABOUT 2.5% BY WEIGHT OF MAGNESIUM WITH SUCH SODIUM-LEAD ALLOY TO ACTIVATE IT AND THEN REACTING SAID TERNARY ALLOY IN THE PRESENCE OF AN ALKYLATING CATALYST HAVING AN ATOM WHICH CHEMICALLYCOORDINATES WITH MAGNESIUM. 